1. Field of the Invention
The present invention relates to an electron emission display, and more particularly, to a structure for supplying a voltage to an anode electrode of the electron emission display.
2. Description of the Related Art
Generally, electron emission elements arrayed on electron emission devices are classified into those using hot cathodes as an electron emission source, and those using cold cathodes as the electron emission source.
There are several types of cold cathode electron emission elements, including Field Emitter Array (FEA) elements, Surface Conduction Emitter (SCE) elements, Metal-Insulator-Metal (MIM) elements, and Metal-Insulator-Semiconductor (MIS) elements.
The MIM element includes first and second metal layers and an insulation layer interposed between the first and second metal layers. In the MIM element, when a voltage is supplied between the first and second metal layers, electrons generated from the first metal layer reach the second metal layer through the insulation layer by a tunneling phenomenon. Among the electrons reaching the second metal layer, some electrons that have a higher energy than a work function of the second metal layer are emitted from the second metal layer.
The MIS element includes a metal layer, a semiconductor layer, and an insulation layer interposed between the metal layer and the semiconductor layer. In the MIS element, when a voltage is supplied between the metal layer and the semiconductor layer, electrons generated from the semiconductor layer reach the metal layer through the insulation layer by a tunneling phenomenon. Among the electrons reaching the metal layer, some electrons that have a higher energy than a work function of the metal layer are emitted from the metal layer.
The SCE element includes first and second electrodes facing each other and a conductive layer disposed between the first and second electrodes. Fine cracks are formed on the conductive layer to form the electron emission regions. When a voltage is supplied to the first and second electrodes to allow a current to flow along a surface of the conductive layer, electrons are emitted from the electron emission regions.
The FEA elements use a theory in which, when a material having a relatively lower work function or a relatively large aspect ratio is used as the electron source, electrons are effectively emitted by an electric field in a vacuum. Recently, the electron emission regions have been formed of a material having a relatively lower work function or a relatively large aspect ratio, such as a molybdenum-based material, a silicon-based material, and a carbon-based material such as carbon nanotubes, graphite, and diamond-like carbon so that electrons can be effectively emitted when an electric field is supplied thereto in a vacuum. When the electron emission regions are formed of the molybdenum-based material or the silicon-based material, they are formed in a pointed tip structure.
A typical electron emission display includes an array of electron emission elements formed on a first substrate and a light emission unit formed on a second substrate. The light emission unit includes phosphor layers and an anode electrode.
The electron emission display includes electron emission regions formed on the first substrate and driving electrodes formed on the first substrate to control the electron emission for each pixel. The anode electrode formed on the second substrate functions to allow the electrons emitted from the electron emission regions formed on the first substrate to be effectively accelerated toward the phosphor layers. Accordingly, the electrons emitted from the electron emission regions excite the phosphor layers to display an image.
The anode electrode receives a direct current voltage of, for example, hundreds through thousands of positive volts that can accelerate the electrons emitted from the first substrate to the second substrate. The voltage is supplied from an input terminal. The input terminal extends from the anode electrode to an edge of the second substrate to be placed external to the vacuum envelope.
Therefore, the second substrate must be provided with a portion on which the input terminal will be disposed. In the conventional electron emission display, one side edge of the second substrate protrudes to provide the portion on which the input terminal will be placed.
The second substrate has an extending portion that extends over the sealing member. The input terminal has a first end contacting the anode electrode and a second end disposed on the extending portion of the second substrate over the seal member.
As described above, in order to supply the voltage to the anode electrode, the second substrate is provided with the extending portion protruding further than the first substrate. This causes an increase of the overall size of the electron emission display.
That is, in the conventional electron emission display, the extending portion of the second substrate functions to only provide the portion for placing the input terminal. The extending portion is a non-active area where the image is not displayed. That is, the extending portion is a dead space that increases the overall size of the display, thereby making it difficult for the display to be compact.